Recently, application of polymer materials to the industrial and medical fields has been developed, and many hydrophilic polymer materials have been used. Particularly, they have been used as polymer materials insoluble to water and having a water-absorbent property, various membranes having a substance-permeable property, catheters, cannulas, sanitary materials, contact lenses, blood preserving containers, blood circuits, cell culture media, or capsules or fixing substrates for enzymes or medicines. Further, such materials can be applied not only to the medical field but also to supports for cataphoresis or liquid chromatography and various coating materials or materials for foods for preventing from fouling or clouding.
In such uses, antifouling property frequently becomes an important factor to the durability and quality of the materials. Especially, in a case where these membranes are used for medical care and brought into contact with blood or body fluid, material components such as platelets, leucocytes, erythrocytes and fibroblasts inevitably adhere thereto, and there are fears that these adhered components generate a thrombus on a surface of a membrane coming into contact with blood and that the components affect a complement. As a result, formation of a thrombus or reduction of an immunity function is presumed to be caused.
As means for solving these problems, a hydrophilic copolymer containing a polyethylene oxide chain was invented (JP-A-SHO-57-164064), and a selectively permeable hollow fiber composed of a copolymer containing an ethylene oxide chain was invented (JP-A-SHO-60-22901). Further, it was found that a semipermeable membrane composed of a hydrophilic acrylonitrile copolymer containing a polyethylene oxide chain and acrylonitrile was excellent in solute permeability and antifouling property (JP-A-SHO-63-130103). Furthermore, a plasma separative membrane excellent in compatibility with blood, which was composed of a mixture of a copolymer containing an ethylene oxide chain and isotactic methyl methacrylate polymer, was invented.
However, in a process for synthesizing a hydrophilic copolymer containing a polyalkylene oxide chain, when copolymerized with an acrylic or methacrylic ester, in a case where the content of polyalkylene oxide in the copolymer is too high, there is a problem that the synthesized copolymer becomes a gel state in spite of the kind of the acrylic or methacrylic ester and it can be hardly dissolved in a solvent. In such a case, it cannot be used as a coating material and cannot be formed as a fiber or a membrane.
Further, even if the content of polyalkylene oxide is low, because the water content of the copolymer copolymerized with acrylic ester or methacrylic ester is low, for example, as compared with that of a copolymer copolymerized with polyacrylonitrile, satisfactory antifouling property and antithrombotic property have not been able to be obtained. As the result of our earnest research to improve the gel structure, a polymer, which can be easily dissolved in a solvent, which has a high water content and which has a high affinity with acrylic ester or methacrylic ester, has been obtained by copolymerizing an acrylic ester or methacrylic ester, polyalkylene oxide and another copolymerizable component.
An object of the present invention is to provide a hydrophilic material which can be dissolved in a solvent and easily molded and which is excellent in antithrombotic property and antifouling property, and further to provide excellent antithrombotic material and semipermeable membrane.